Cotton
Not much has changed over the past week with the cotton
situation. We are still fighting bugs in some fields statewide, while other
fields are relatively clean. A little cotton is starting to open, while most of
it isn’t quite out of the woods yet. We have talked to several folks that are
starting to put out a “clean up” shot then walking away. Keep in mind that our
stink bug threshold bumps up to 30-50% internal boll damage during the 7th
and 8th weeks of bloom. This is because there aren’t as many
susceptible bolls left in the field. They key thing to remember with stink bug
management is that they can damage a boll until it is about 25 days old. So, we
need to protect bolls we plan to harvest until the are at that point.
We continue to hear that the spider mite situation in the
Wiregrass just won’t go away. Research from the mid-south says you can stop
spraying spider mites at NSWF 5 + 350 heat units (likely somewhere around NWAF
2 or 3). Based on my experiences in the mid-south, and my short time working
with cotton insects in Alabama, I think we need fight a little longer than “cutout”
in the Wiregrass. In areas where the top crop plays a significant role in the
yield potential of the crop, we need to protect from spider mites until we feel
those bolls are filled. Spider mites damage cotton by sucking nutrients out of
the leaves and can cause premature defoliation. In these situations, if we don’t
get all the necessary photosynthate from the leaf to the boll, we will see yield
losses. While it sounds like some control options are getting harder to locate,
we do have several options (abamectin, Zeal, Portal or Oberon).
We are hearing reports of high flushes of bollworm moths in
some fields across the state. We have also heard about some 2–3-day old worms
found under bloom tags. To date, we have not heard of any issues with escaped
worms in our 2-gene cotton (outside of 2017) or in our 3-gene cotton (at all). We
also plant Bt sentinel plots across the state and se have not observed any
issues with control in those plots either. We do not recommend treating bollworms
based on eggs for this reason. We are paying a premium for these technologies
so let’s give them a chance to work.
One final note on cotton, the silverleaf whitefly situation in
Georgia is beginning to move west. We are hearing about fields being treated
near the Alabama line and have received a report of SLWF in at least one field
in Alabama. This will not be a widespread issue across the state but can have
major impacts on cotton in the historic SLWF area. We will go into full details
on SLWF as the situation evolves, but just to give a brief refresher:
· Late planted cotton is at a greater risk
· Threshold: 50% of leaves (5th node from terminal) are infested with 5+ immatures per lea
Immature SLWF resemble aphids, however if you rub the bottom of the leaf on your shirt SLWF will stay on the leaf and aphids will rub off
·
Insect growth regulators (Knack and Courier) are
the backbone of SLWF management, but they must be applied timely (i.e. early)
Soybean
We are beginning to pick up looper and velvetbean
caterpillar populations in fields. In some cases, defoliation is reaching 15-20%
and treatments are going out. Scout to make sure you know which species are in
the mix to make the proper insecticide selection. We have received reports of velvetbean caterpillars in fields in the TN Valley as well. We don't often get VBC that far north. We had several fields sprayed in 2020 but it had been quite a while prior to that. VBC are easily managed with most labeled insecticides, but they have every bit the damage potential as soybean looper and should be given the same attention.
The redbanded stink bug situation is still building as well.
Once the immatures start to develop in fields, they can be difficult to get
back under control. Two-way tank-mixtures of pyrethroids, acephate and/or
neonics are necessary. If we come out swinging early, we can manage them.
Things get difficult when populations build and are left unchecked too long.
Deer Survey
In response to a farmer request, the Alabama Extension
Agronomics Crops Team is conducting a survey to better understand the impacts
of deer population on crop production. Please take a few moments to help us
collect information to try to use to figure out ways to mitigate deer losses in
your row crops.
You can take the anonymous survey here (link).
If you would like to provide reports or observations on the insect situation from your region, please let us know. You can reach Scott Graham at 662-809-3368 or scottg@auburn.edu or Ron Smith at 334-332-9501 or smithrh@auburn.edu.
As always, if we can ever be of any help, please let us know.
